The present invention relates to information storage and, more particularly, to a storage system and a method for managing the storage system enabling external apparatuses to use data storage devices in the storage system.
In the recent computer environment, the amount of user data and information has rapidly increased, particularly with the Internet where it has come to be commonly used in an explosive fashion. Consequently, the amount of data to be stored is increasing. One of typical example of a data storage device is a magnetic disk storage (hereinafter referred to as a drive). At present, the growth of the amount of data to be stored is greater than the increase in the recording density of the drive.
Therefore, the number of drives used by users increases year by year and the number of drives mounted in a large-scale storage system is estimated to reach several thousands and more in the future. If, for example, we intend to realize a storage system with capacity of the order of petabytes using drives with capacity of several hundreds of gigabytes per drive, the required number of the drives will be on the order of several thousands. In this situation, the cost of managing data that increases day by day continues to rise and the reduction of such management cost is an important problem.
From the viewpoint of managing storage devices (drives), if a great number of devices are distributed and located, consolidated management thereof is impossible. If a small number of devices are collectively located, consolidated management thereof is simpler and management cost can be reduced.
As a conventional storage system, a disk subsystem is known. Lately, a storage area network (hereinafter abbreviated to SAN) and network attached storage (hereinafter abbreviated to NAS) have attracted attention.
An example of such conventional storage system is shown in FIG. 22. Disk subsystems 101, 111 and NAS 120 are roughly composed of a control section and a data storage section. For example, a disk subsystem includes a disk controller that is comprised of a channel control section for data input/output from/to a host, a cache, and a disk control section for controlling drives and a disk drive cluster consisting of a plurality of drives. Although the drives may be referred to hard disks or simply disks, the term drives is used hereinafter.
The NAS includes a local area network interface (hereinafter abbreviated to LANIF) for data input/output from/to a host, a cache, a disk control section for controlling drives and a plurality of drives. While the drives are exemplified as the units in the data storage section in the above drawing, disk arrays, each consisting of a plurality of drives, may be employed.
Meanwhile, the SAN is a network provided between hosts and the disk subsystem and is generally embodied with fiber channels. The SAN facilitates sharing the same disk subsystem across a plurality of hosts.
Consequently, the disk subsystems separately connected to each host are connected to the hosts via the SAN, thereby making it possible to integrate them into a storage system. In other words, a great number of small and medium scale disk subsystems that are distributed are organized into a small number of large scale consolidated disk arrays. Thus, consolidated data management can easily be carried out and the management cost can be reduced.
For such conventional storage system, however, the scalability in performance and capacity is not sufficient. This is because the control section and the data storage section of the conventional storage system are provided as fixed integral parts.
For the conventional storage system, for example, the number of drives that can be mounted per system is fixed and this number determines the capacity that can be provided by system. Therefore, if a client needs capacity more than the capacity that can be provided by a single disk subsystem, whereas requiring lower performance, a plurality of disk subsystems must be prepared. If a client needs performance higher than the performance that can be provided by a single disk subsystem, while requiring smaller capacity, a plurality of disk subsystems must be prepared. Consequently, a great number of storage systems are installed and this makes the management thereof complex.
In order to enhance the scalability while avoiding the rise of the cost of managing several thousands of drives and more, it is necessary to centralize the management of the drives. In attempting to simply enhance the scalability of a single disk subsystem, however, the control section is a bottleneck in performance.
To achieve enhanced scalability in performance and capacity, it is desirable to expand the disk controllers and the drives separately. To accomplish this, by connecting the disk controllers and drives via a network or switch, high scalability can be obtained. An example of such a known technique is disclosed in, for example, JP-A-11-296313 (hereinafter referred to as Reference 1).
One problem addressed by the present invention is to alleviate the burden of managing expanding user data and reducing the data management cost, which has not been solved by the above-mentioned technique.
In the conventional disk subsystem, the disk controller and the disk drive cluster that constitute the subsystem are fixed and there are limitations of scalability in performance and capacity. To achieve the scalability beyond the limit, a plurality of disk subsystems must be prepared which further increases management cost.
Reference 1 discloses connecting the disk controller and the disk drive cluster via a network or switch. However, centralized management of the drives is not described in Reference 1. Because disk controllers each separately manage drives, consolidated management of drives is impossible. When managing several thousands of drives and more, the management is complex. In addition, there is no description of drive reconfiguration management such as adding drives and copying data from drive to drive in Reference 1.